<div>
  If you are not using inbound agents, it's recommended that you disable this
  entirely, which is the default installation behavior. Jenkins uses a TCP port
  to communicate with agents connected inbound. If you're going to use inbound
  agents, you can allow the system to randomly select a port at launch (this
  avoids interfering with other programs, including other Jenkins instances). As
  it's hard for firewalls to secure a random port, you can instead specify a
  fixed port number and configure your firewall accordingly.
</div>
